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THE MENSTRUAL CYCLE
Sevag Ouzounian
Overview
• Menstrual cycle has evolved to follow lunar cycle – 28
days. This however varies month to month and can be
diff...
Overview
• Necessities for normal menstrual cycle
• Intact hypothalamo-pituitary-ovarian axis
• Responsive follicles in ov...
Hormone Control of Cycle
• Hypothalamo-pituitary-ovarian axis
• Cycle controlled by hypothalamus,
however this can be infl...
Hormone Control
• Follicular stimulating hormone (FSH) – glycoprotein
• Stimulates follicular maturation during follicular...
Ovarian Cycle – Follicular Phase
• Days 1-8 – FSH and LH relatively
high levels
o Stimulate development of 10-20 follicles...
Ovarian Cycle – Follicular Phase (2)
• Days 9-14 –
o Follicle increases in size
o Localized accumulation of fluid among
gr...
Ovarian Cycle - Ovulation
• Day 14 – rapid enlargement of follicle
and rupture of the follicle with extrusion
of the oocyt...
Ovarian Cycle - Luteal Phase
• Days 15-28 – remainder of the
follicle retained in the ovary –
penetrated by capillaries an...
Ovarian Cycle
• If conception and implantation occur:
• Corpus luteum doesn’t regress – maintained by gonadotrophins
secre...
Ovarian and Uterine Cycle
Uterine Cycle
• Influenced by the cyclical
production of steroid
hormones
• Causes changes to the uterus
• Involving the e...
Uterine Cycle – Endometrium Overview
• Two layered
• Superficial layer that sheds during the menstrual cycle
• Basal layer...
Uterine Cycle – Proliferative Phase
• Occurs during follicular phase
of ovarian cycle
• Endometrium exposed to
oestrogen ...
Uterine Cycle – Secretory Phase
• After ovulation – progesterone
production causes secretory
changes in endometrial glands...
Uterine Cycle – Menstrual Phase
• Luteal phase lasts 14 days –
then there is a regression of
corpus luteum  decline in
oe...
Cervical Mucus
• Important to stop ascending infection
• Changes during the menstrual cycle
• Early follicular phase – vis...
Other Changes
• Body temperature – Rise of 0.5°C after ovulation till onset
of menstruation. Due to progesterone levels. I...
Menses
• Production of 35-80ml of blood
• Over an average of 3-5 days
References
• Majority of information from
• Drife, J. & Magowan, B. (2008). The normal menstrual cycle,
Clinical Obstetric...
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Menstrual Cycle

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Menstrual Cycle

  1. 1. THE MENSTRUAL CYCLE Sevag Ouzounian
  2. 2. Overview • Menstrual cycle has evolved to follow lunar cycle – 28 days. This however varies month to month and can be different in different women • There is the uterine cycle and the ovarian cycle • Cycle composed of • Follicular phase • Ovulation • A postovulatory or luteal phase
  3. 3. Overview • Necessities for normal menstrual cycle • Intact hypothalamo-pituitary-ovarian axis • Responsive follicles in ovaries • Functional uterus • If cycle is prolonged • Follicular phase will lengthen • Luteal phase will remain constant at 14 days
  4. 4. Hormone Control of Cycle • Hypothalamo-pituitary-ovarian axis • Cycle controlled by hypothalamus, however this can be influenced by higher centres within the brain • i.e. due to stress or anxiety • Hypothalamus releases gonadotrophin-releasing hormone in pulsatile manner  anterior pituitary  release of LH and FSH
  5. 5. Hormone Control • Follicular stimulating hormone (FSH) – glycoprotein • Stimulates follicular maturation during follicular phase • Stimulates steroid hormone secretion – oestrogen (by the granulosa cells of mature ovarian follicle) • Lutenizing Hormone (LH) – glycoprotein • Stimulates steroid hormone secretion – oestrogen • Ovulation – mid-cycle surge of LH • Progesterone production by corpus luteum • Negative feedback mechanism controls cycle
  6. 6. Ovarian Cycle – Follicular Phase • Days 1-8 – FSH and LH relatively high levels o Stimulate development of 10-20 follicles o Results in full maturation of a single dominant follicle – appearing in mid- follicular phase o Remainder undergo atresia o High LH and FSH triggered by drop in oestrogen and progesterone levels from last cycle . o Oestrogen levels start to rise as follicular development occurs
  7. 7. Ovarian Cycle – Follicular Phase (2) • Days 9-14 – o Follicle increases in size o Localized accumulation of fluid among granulosa cells  fluid-filled central cavity called antrum o Transforming primary follicle to Graafian follicle o Oocyte occupies excentric position – surrounded by cumulus oophorus – 2-3 layers of granulosa cells o Rise in oestrogen by granulosa cells, associated with follicular maturation o Inhibin produced by granulosa cells – restricting number of follicles maturing
  8. 8. Ovarian Cycle - Ovulation • Day 14 – rapid enlargement of follicle and rupture of the follicle with extrusion of the oocyte and adherent cumulus oophorus • Some women get pain before rupture – called Mittelschmerz • Rise in oestrogen  mid-cycle surge of LH and to a lesser extent FSH  ovulation • Immediately before ovulation there is a drop in oestrogen and an increase in progesterone. • Ovulation follows within 18 hours of mid- cycle surge of LH • If not enough of a LH surge – then no ovulation occurs – anovulatory
  9. 9. Ovarian Cycle - Luteal Phase • Days 15-28 – remainder of the follicle retained in the ovary – penetrated by capillaries and fibroblasts from the theca • Grunlosa cells undergo luteinization  corpus luteum formation – the major source of sex hormones – oestrogen and progesterone secreted during postovulary phase • This leads to marked increase in progesterone and oestrogen
  10. 10. Ovarian Cycle • If conception and implantation occur: • Corpus luteum doesn’t regress – maintained by gonadotrophins secreted by trophoblasts • If conception doesn’t occur successfully: • Corpus luteum regresses and menstruation occurs • Drops in steroid sex hormones  leads to a rise in gonadotrophin levels (FH and LSH)  initiate next cycle
  11. 11. Ovarian and Uterine Cycle
  12. 12. Uterine Cycle • Influenced by the cyclical production of steroid hormones • Causes changes to the uterus • Involving the endometrium and cervical mucus
  13. 13. Uterine Cycle – Endometrium Overview • Two layered • Superficial layer that sheds during the menstrual cycle • Basal layer that doesn’t take part, but regenerates the superficial layer • The basal layer has straight arterioles where as the superficial layers has spiral ones – important in the process of shedding
  14. 14. Uterine Cycle – Proliferative Phase • Occurs during follicular phase of ovarian cycle • Endometrium exposed to oestrogen  regeneration from the last menstrual cycle • Glands in endometrium are straight in this phase, parallel to one another and contain little secretion
  15. 15. Uterine Cycle – Secretory Phase • After ovulation – progesterone production causes secretory changes in endometrial glands • Appearance of secretory vacuoles in glandular epithelium below nuclei • Secretions in lumen of glands  which become tortuous and develop serrated margins
  16. 16. Uterine Cycle – Menstrual Phase • Luteal phase lasts 14 days – then there is a regression of corpus luteum  decline in oestrogen and progesterone • This leads to a intense spasmodic contraction of spiral section of endometrial arterioles  ischaemic necrosis  shedding of superficial layer  bleeding. • These spasms are associated with prostoglandin, which are also associated with increased uterine contractions during menstrual flow.
  17. 17. Cervical Mucus • Important to stop ascending infection • Changes during the menstrual cycle • Early follicular phase – viscid and impermeable • Late follicular phase – increasing oestrogen levels  mucus becomes watery and easily penetrated, allowing spermatozoa to get through. Change is known as Spinnbarkheit • Post-ovulation – progesterone from corpus luteum counteracts oestrogens effects  mucus becomes impermeable and the cervical os contracts
  18. 18. Other Changes • Body temperature – Rise of 0.5°C after ovulation till onset of menstruation. Due to progesterone levels. If conception occurs – this temperature is maintained throughout pregnancy • Breast changes – breast swelling during luteal phase due to increasing progesterone levels • Psychological changes – change in mood and an increase in emotional lability. Might be due to falling progesterone levels.
  19. 19. Menses • Production of 35-80ml of blood • Over an average of 3-5 days
  20. 20. References • Majority of information from • Drife, J. & Magowan, B. (2008). The normal menstrual cycle, Clinical Obstetrics and Gynaecology, Ch11, pp. 121-126 • All images from google.com/images

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